119 lines
3.8 KiB
C++
119 lines
3.8 KiB
C++
/* boost random/seed_seq.hpp header file
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*
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* Copyright Steven Watanabe 2010
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* Distributed under the Boost Software License, Version 1.0. (See
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* accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*
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* See http://www.boost.org for most recent version including documentation.
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*
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* $Id$
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*
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*/
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#ifndef BOOST_RANDOM_SEED_SEQ_HPP
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#define BOOST_RANDOM_SEED_SEQ_HPP
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#include <boost/config.hpp>
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#include <boost/cstdint.hpp>
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#include <boost/range/begin.hpp>
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#include <boost/range/end.hpp>
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#include <cstddef>
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#include <vector>
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#include <algorithm>
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#include <iterator>
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#ifndef BOOST_NO_CXX11_HDR_INITIALIZER_LIST
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#include <initializer_list>
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#endif
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namespace boost {
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namespace random {
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/**
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* The class @c seed_seq stores a sequence of 32-bit words
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* for seeding a \pseudo_random_number_generator. These
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* words will be combined to fill the entire state of the
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* generator.
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*/
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class seed_seq {
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public:
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typedef boost::uint_least32_t result_type;
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/** Initializes a seed_seq to hold an empty sequence. */
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seed_seq() {}
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#ifndef BOOST_NO_CXX11_HDR_INITIALIZER_LIST
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/** Initializes the sequence from an initializer_list. */
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template<class T>
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seed_seq(const std::initializer_list<T>& il) : v(il.begin(), il.end()) {}
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#endif
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/** Initializes the sequence from an iterator range. */
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template<class Iter>
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seed_seq(Iter first, Iter last) : v(first, last) {}
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/** Initializes the sequence from Boost.Range range. */
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template<class Range>
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explicit seed_seq(const Range& range)
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: v(boost::begin(range), boost::end(range)) {}
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/**
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* Fills a range with 32-bit values based on the stored sequence.
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*
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* Requires: Iter must be a Random Access Iterator whose value type
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* is an unsigned integral type at least 32 bits wide.
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*/
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template<class Iter>
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void generate(Iter first, Iter last) const
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{
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typedef typename std::iterator_traits<Iter>::value_type value_type;
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std::fill(first, last, static_cast<value_type>(0x8b8b8b8bu));
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std::size_t s = v.size();
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std::size_t n = last - first;
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std::size_t t =
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(n >= 623) ? 11 :
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(n >= 68) ? 7 :
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(n >= 39) ? 5 :
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(n >= 7) ? 3 :
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(n - 1)/2;
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std::size_t p = (n - t) / 2;
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std::size_t q = p + t;
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std::size_t m = (std::max)(s+1, n);
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value_type mask = 0xffffffffu;
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for(std::size_t k = 0; k < m; ++k) {
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value_type r1 = static_cast<value_type>
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(*(first + k%n) ^ *(first + (k+p)%n) ^ *(first + (k+n-1)%n));
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r1 = r1 ^ (r1 >> 27);
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r1 = (r1 * 1664525u) & mask;
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value_type r2 = static_cast<value_type>(r1 +
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((k == 0) ? s :
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(k <= s) ? k % n + v[k - 1] :
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(k % n)));
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*(first + (k+p)%n) = (*(first + (k+p)%n) + r1) & mask;
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*(first + (k+q)%n) = (*(first + (k+q)%n) + r2) & mask;
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*(first + k%n) = r2;
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}
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for(std::size_t k = m; k < m + n; ++k) {
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value_type r3 = static_cast<value_type>
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((*(first + k%n) + *(first + (k+p)%n) + *(first + (k+n-1)%n))
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& mask);
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r3 = r3 ^ (r3 >> 27);
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r3 = (r3 * 1566083941u) & mask;
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value_type r4 = static_cast<value_type>(r3 - k%m);
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*(first + (k+p)%n) ^= r3;
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*(first + (k+q)%n) ^= r4;
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*(first + k%n) = r4;
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}
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}
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/** Returns the size of the sequence. */
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std::size_t size() const { return v.size(); }
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/** Writes the stored sequence to iter. */
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template<class Iter>
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void param(Iter out) { std::copy(v.begin(), v.end(), out); }
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private:
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std::vector<result_type> v;
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};
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}
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}
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#endif
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